1. Field of the Invention
The invention relates generally to a rice polishing machine, and particularly to a horizontal rice polishing machine of the type described hereinafter, the machine including a housing with a shaft mounted essentially horizontally therein, a drive coupling member carried on one end of the shaft, and a polishing-rotor carried on the other opposite end of the shaft, a conveyor screw coaxially and fixedly connected to the polishing-rotor, and a screen housing surrounding the polishing-rotor at a distance so as to form an annular space therebetween for cooperation with the conveyor screw. The housing is also provided with a rice feed orifice at the conveyor screw and with a rice discharge orifice at the edge thereof remote from the conveyor screw. A funnel member is also provided underneath the screen housing for collecting and discharging the polishing powder.
2. Description of the Prior Art
Such machines having a cylindrical polishing rotor are known. The polishing surface of the polishing rotor is formed by an exchangeable casing. This wears away during use and therefore has to be replaced after a certain time. Consequently, the rotor should be easily accessible and easy to remove for maintenance purposes. In known rice-polishing machines, however, the construction of the rotor is complicated, because various parts of the housing have to be removed before the rotor becomes accessible and because the rotor has to be released from its shaft for dismantling. Furthermore, it is desirable if the distance between the polishing rotor surface and the screen housing surrounding the rotor is readjustable. This distance determines, in addition to other parameters, the polishing properties of the machine, so that these change with increasing wear of the rotor. However, the cylindrical rotors used on horizontal rice-polishing machines do not allow such readjustment. It is considered that the outlay on horizontal machines which is necessary to allow readjustability is not justified because these machines generally offer only relatively low polishing quality in comparison with vertical rice-polishing machines, and consequently slight variations in the polishing quality, such as are caused by a varying distance between the rotor surface and the surface of the screen housing, are not important. Conical rotors which can be adjusted axially to set the distance from the screen housing are known only in vertical rice-polishing machines. However, even in the vertical machines, these rotors are very difficult to dismantle because a large number of housing parts must be removed and either the bearings or the rotor have to be released from the shaft. The housing structure of vertical machines is by the very nature of their system substantially more complicated than that of horizontal machines, this being connected with the arrangement of the feed and discharge orifices. Although they generally give a higher polishing quality, nevertheless because of the complications mentioned they are more expensive and present considerable difficulties as regards maintenance, so that horizontal machines are frequently preferred in less technically advanced areas of rice cultivation. Finally, the known rice-polishing machines have the disadvantage that, in addition to a mechanical drive which can be supplied from an electric motor or an internal combustion engine, they also have a fan which generally requires a supply of electrical power. This also can be troublesome for practical application in less technically advanced areas.